Point of fact - not almost zero. Literally zero. The way troop drops works is that a type is rolled (troop, or “other”) and if troop is rolled a rarity is rolled, and then a troop is rolled from that rarity. Pharos was available as a drop in the event key pool, but the chance to pull a mythic from an event key if you rolled a troop was set to zero (85% UR, 12% epic, 3% legendary for those 4 hours instead of the correct 84.88% UR, 12% epic, 3% legendary, 0.12% Mythic), making him impossible to draw. The same thing appears to have happened during Forest of Thorns event - YC was in the event key drop pool, but the chance to draw a mythic from an event key was also set to zero, meaning she was impossible to draw.